In mechanical systems monitoring of components can be very important. For example, roller bearings may suffer from abrasion and may cause severe damage to mechanical systems when they break down. Therefore, the deterioration of these components can be monitored using transducers or sensors. Such sensors may provide piezoelectric components or semiconductors, which convert a mechanical or acoustic vibration or oscillation into an electrical signal. The electrical signal can then be processed, for example, a frequency analysis can be carried out, in order to detect frequencies which indicate an abrasion or deterioration of the respective components. For example, a roller bearing, as it wears out, may generate characteristic vibrations, which, once detected, may indicate a forthcoming breakdown of the bearing. Such a signal can then be used to generate a warning, especially when further components will be affected by the bearing breakdown.
The application of bearings and according monitoring systems as described above is very broad. For example, any kind of vehicles use a large number of bearings, such of which are used to bear critical components. For example, thinking of trains, their axes make use of bearings, which may cause severe accidents and damages, when they break down. Another application is, for example, power plants, such as off-shore wind power stations. The bearing of the rotors of such power stations is critical, especially when they are located off-shore, i.e. when they are not easily accessible. Therefore, there is a desire to monitor the bearing of such wind power stations in order to detect eventual failures early and to shut down the power station before severe damages occur. Steel works are another example of an application of the above transducer systems. Wherever bearings are used to bear components of power units, may they be rotors of wind power stations, axes of combustion engines or engines of conveyor belts, there is a desire to be informed of a forthcoming failure as soon as possible.
Document U.S. Pat. No. 3,663,842 A discloses an ultrasonic probe, which has a solid, flexible, elastic, graded acoustical impedance coupling device with fine geometrical and naturally shaped metal and glass component powders. Document GB 2 109 555 A discloses an ultra-sound transducer, which is coupled to a work piece by an elastomeric member and measurements based on echoes returned from inhomogeneities within the work piece are initiated by detection of the echo from the interface between the work piece and the coupling member.